For the purpose of energy conservation, reduction of carbon dioxide (CO2) and the like, electromagnetic motors are required to have further enhanced performances, and these performances represented by reduced size and weight, higher efficiency, higher torque, and higher power have been dramatically enhanced on a daily basis. Electromagnetic motors can be broadly classified into (1) radial flux motors, (2) axial flux motors, and (3) transverse flux motors, based on magnetic flux direction.
Among these types, radial flux motors are excellent especially in cost performance, and have been widely used for various products in the industrial community as representative machine elements of general-purpose actuators. In addition, axial flux motors are structurally characterized in that they can be adapted to complex three-dimensional magnetic circuit configurations whereas it is difficult to use laminated steel plates, which have been commonly used, in such applications. Axial flux motors are applied, in particular, in the fields of medium/large-sized large-diameter thin motors.
Furthermore, transverse flux motors each include an armature (configuring a divided toroidal core), as a basic unit, constituted by a rotor including permanent magnets, a circular coil formed about a rotation axis of this rotor, and a plurality of stator cores each having a substantial U shape (hereinafter, referred to as U-shaped stator cores) that are provided on a circumference about the rotation axis so as to surround the circular coil. Transverse flux motors are characterized by their configuration in which two or more of the basic units are muitistaged along the rotation axis at a predetermined relative phase angle about the rotation axis, which can relatively simply achieve a higher torque due to the multipolarization and high-efficiency magnetic field generation due to the divided toroidal core structure.
Radial flux motors and axial flux motors each need a stator core including a plurality of slots on a circumference about a rotation axis, coils wound around the these slot portions, and a dead space for assembling and inserting the coils and the like. In contrast, transverse flux motors are generally easy to multipolarize because the multipolarization can be made only by providing a plurality of U-shaped stator cores on the circumference about the rotation axis.
In addition, since an armature constituted by the circular coils and the U-shaped stator cores (divided toroidal cores) has a structure in which magnetic flux generated from the coil hardly leaks outside, magnetic field generation efficiency by the coils is high, and downsizing thereof can be expected as compared with radial flux motors and axial flux motors including coil ends.